The risk for malignant lymphoma (including non-Hodgkin's lymphoma, Hodgkin's disease, and chronic lymphocytic leukemias associated with immune modulation-- i.e., conditions and exposures that alter the immune system. Different subgroups lymphomas have different risk factors. Dr. Hans-OIov Adami and Dr. Mads Melbye are leading a population-based case-control study to investigate the etiology of lymphoma in Sweden and Denmark. A total of about 3,400 patients and 3,000 controls were recruited into the study between October 1999 and October 2002. Through a rapid case ascertainment system, the cases were identified shortly after diagnosis. The controls were randomly selected from national population registers and frequency-matched to the cases by sex and age. Both cases and controls have completed telephone-based questionnaires that elicited detailed information on exposures such as earlier medical conditions including infectious diseases, drug use and blood transfusions, UV light, and socio-economic factors and lifestyle. Blood samples were collected in order to assess the importance of viral exposures (EBV and HTLV-I). Tumor material from the cases has been reexamined and uniformly classified according to the REAL classification. [unreadable] [unreadable]